Drying oven for printed metal sheets



May 15, 1 923. 1,455,540

C. E. M MANUS DRYING OVEN FOR'PRINTED MET-AL SHEETS Filed Deb. 2 1921 5 Sheets-Sheet 1 M X & m\& A X CA a avwwnto'c May 15, 1923.

C. E. M MANUS DRYING OVEN FOR PRINTED METAL SHEETS Filed Dec. 29 1921 3 Sheets-Sheet 2 T 3 emtoz & M

35 5 Hem m May 15, 1923.

' c. E. M MANUS DRYING OVEN FOR PRINTED METAL SHEETS Filed Dec. 29 1921 3 SheetsSheet 5 county, and State of New Patented May 15, 1923.

rmuana'r OFFICE.

CHARLES E. MCMANUS, OF NEW YORK, N. Y.

DRYING OVEN FOB, PRINTED METAL SHEETS.

Application filed December 29, 1921. Serial No..525,806.-

To all whom it may concern:

Be it known that 1, Cinemas E. MGMANUS,

a citizen of the United States, residingat the borough of Manhattan York, have 1nvented certain new and useful Improvements in Drying Ovens for Printed Metal Sheets, of which the following is a specification, reference being had therein to the acoompanying drawings, which form a part thereof.

-My invention relates to drying ovens for printed metal sheets, and more particularly to a type thereof wherein the sheets are conveyed y a sequence of travelling racks at a low speed through a housing containing heating elements, ordinarily gas burners,

being delivered, at one end of the oven to said racks and removed therefrom at the other end of the oven.

Such ovens have been commonly used for drying the vehicle in the ink, or other coating material, upon printed sheets, it having been the common practice to provide an oven housing open at both ends and having a sequence of gas burners in the bottom thereof.

With ovens ofthe type heretofore used, the process of drying the ink was very slow, thus involving the use of ovens of great length, the slowv drying resulting from the n used as a one way, or a return way, oven, in

reduced, requiring the subjecting of the sheets for a longer period to the action of the gases within the oven. This condition also resulted in the heating of the metal plates to a temperature in excess of that actually required to secure a rapid oxidation of the coating thereuponfso as to make the handling of the plates difiicult at the discharge end of the oven and in some instances give an unsatisfactory finish to the sheets.

, With the above conditions in mind, I have produced a drying oven wherein no products of combustion are admixed with the air which is circulated about and in contact with V the printed, or otherwise coated, plates, thus in the city,

mitting the use of very much shorter ovens, and a higher speed in the traverse of the racks, giving increased capacityper lineal foot of the oven structure.-

In addition to preventing contact of prodacts of combustion with the plates being dried, I so construct an oven embodying my invention as to maintain a continuous circulation of heated, pure. air about and between the succeeding plates upon the carrier racks, thus avoiding the accumulation of fumes, given off by the coating material during heating and oxidation, in the oven and preventing the pocketing of air and such fumes between and in contact with the surfaces of adjacent plates.

In addition to the advantages above secured, I so construct the oven that acooling. draft of pure air is delivered adjacent the discharge point of the oven with the two-- which case both reaches of the conveyer rack structure may be utilized, thus doubling the capacity of the oven.

The invention conslsts primarily in a dry ing oven for metal sheets embodying therein an elongated housing, an endless carrier adapted to. receive low speed traverse therethrough and including a sequence of racks closelyjuxtaposed and adapted to receive at spaced intervals, coated metal sheets, an enclosed heating unit within said housing, means withdrawing the products of combustion from said heating unit and discharging. them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented; and means circulating air about said heating unit and within said housing and discharging it externally of the oven, whereby fumes developed inthe oxidation of the coating material upon said sheets are removed fromadjacent the sheets and. from within the oven, and a. continuous circulation of fresh, heated air is maintained about" the sheets;

' ticularly showing the arrangement of the heating units, the means of withdrawing the prod-' ucts of combustion therefrom, and the means for circulating heated air throughout the oven;

Fig. 4 is an enlarged section on the line 4 4 of Fig. 3;

Fig. 5 is a cross-sectional view on the line 55 of Fig. 4, of one of the heating units;

Fig. 6 is a side elevation of the other end of the oven; and A Fig. 7 is an enlarged cross-sectional View on the line 77 of Fig. 6.

Like letters refer to like parts throughout the several views.

In the embodiment of my invention shown in the drawings, a indicates the housing of an oven having mountedtherein upon suitable tracks bb', endless carrier chains cc having movement upon said tracks, the upper reach of said chains respectively co-operating with the tracks b, and the lower reach of said chainsrespectively with the tracks 6. Said chains are driven in the usual manner at any desired speed which will afford ample time for an adequate drying of the coating upon the sheets while they are within the oven a.

The ends of the housing a are open to permit an unobstructed passage of the hooked racks d a sequence of which are carried by the chains 0-0 in sufiiciently close juxtaposition to give the desired capacity to the oven with a given speed of said chains c/;.

The books 03 upon each of the racks d are provided so as to permit the lower reach of the chains to be utilized for carrying metal sheets.

This construction is old and well known in the art, my invention relating more particularly to the embodiment in a mechanism of this t e of means whereby heated air may be e ivered to the oven housing without having commingled therewith the prod- .ucts of combustion from the heating units,

and means whereby the fumes given forth as a result of the heating and oxidation of the coating material, are prevented from ac-' cumulating in said housing by a circulation inducing mechanism, which will ensure a continuous flow of heated, pure air through the housing in a manner to prevent pocketing of accumulated fume-laden air between, and in contact with, the surfaces of succeeding plates.

Located adjacent the bottom of the housing a is a plurality of heating units e, the number of such units being determined by the length of the housing and the temperature required to secure an effective oxidation or drying of the coating material. Each of these units is identical with every other, so that a detail description of but one of them is necessary, corresponding reference letters being applied to other units where they appear in the drawings.

Each heating unit comprises a casing e communicating with atmospheric air adjacent the bottom of the housing through the opening a through the wall of the housing. The casing e has a plurality of openings 6 extending transversely of the top thereof, said top being imperforate except for said openings e Within the casing e is a plurality of boxes f, f and f one of which as) communicates with atmosphere, said boxes being in communication with each other through tubes 9 alternately arranged at opposite ends of said boxes so as to permit the heat and heated gases to circulate through the entire series of boxes, the last box, as F, being in communication through the pipe g with a fuel pipe 9 By arrangin said flue pipe 9 and said pipes 9 within t e housing a, I am enabled to take advantage of the radiant heat therefrom in maintaining the desired temperature within the housing a. The boxes f, f, f and f are supported above the opening a and are spaced apart with relation to each other so' as to cause the infiowing air to pass about the bottom, sides and ends of each box, the openings e being positioned above the substantially vertical centers of said boxes so as to cause the air to pass over each box before it is permitted to escape into the oven. In this manner the entire surface of each box is utilized in bringing the air to the desired temperature, thus securing not only economy in the operation of the heatin unit, but ensuring an adeuate volume of resh air at all times within ,t e housing a.

'unit e.

Extending within the housing a adjacent the to thereof is an ofitake duct 71 having a plural ty of openings as i presented toward the travelling racks (i, said oiftake duct having in the length thereof a suction ump i which is operating continuously wl iile the ducing a circulation of air about the heating units 6 and throughout said housing and preventing the pocketing of air between the metal plates upon the racks d. The pump 21 has no function in removing the products of combustion from the heating units.

By the construction heretofore described, the metal plate adjacent each rack d has the entire surface of both sides thereof constantly brought in contact with a moving current of pure, heated air, the temperature of each plate being gradually raised as it progresses through the oven, the heating of the plate and of the coating thereon, as well as the heating of the air, increasing the effectiveness of the oxidizing action of the oxygen of the air upon said coating.

I have, in actual practice, found it desirable to cause a sudden drop in the temerature of the plates before they-reach the delivery end of the oven, the advantages being two-fold; the cooling of the plates so that they may be readily handled by the operator at the discharge end, and a hardening action upon the coating material, so that after a plate has been removed from the oven, it may be stacked with other plates without any possibility of the scratching of the coated surface thereof.

To secure the desired result without'unnecessary lengthenin of the oven structure to permlt traverse o the plates in the open air after they leave the high temperature zone of the housing a, I provide adjacent the end of said housing and beyond the last burner unit, a blower structure adapted to direct atmospheric air between the plates upon succeeding racks. This blower structure consists of a shell j upon one side of the housing a and communicating therewith through an opening in the wall of said housing, the bottom" of said shell being curved as shown and the upper portion thereof having a top closure j forming an opening at a point of the shell most remote from the housing a. The ends of said shell are closed, and rotatably mounted therein is a fan k having a lurality of radially extending blades. aid fan is actuated at high speed by means of the motor m.- .The shell j and the fan is are of considerable length so as to subject the plates to a blast,

of atmospheric air at normal temperature, for a considerable period, particularly when the low rate of traverse of the sheet is considered Directly opposite the opening through which the fan is discharges air into the housing a, is a hood n leading from which is a flue 12. having a discharge opening externally of the housing a so that the. air used for cooling purposes and any fumes mixed therewith may be delivered exteriorly of the oven and of the room in which the oven is situated.

In the embodiment of the invention shown in the drawings, which is a direct and a return reach or two-way oven, I provide.

similar blower structures, one adjacent each end of the housing a, that at one end being opposite the racks upon the upper reach of the chains, and that upon the other being opposite the racks upon the lower reach of the chains. A horizontal partition 0 is positioned between the two reaches of the chain throughout the entire length of each blower structure, so as to limit the actionof the blower to the sheets upon one reach only of the carrier.

In the accompanying drawings I have used the same reference letters in connection with each of the blower structures, since they are identical in construction and mode of operation, different one from the other, merely in their location with relation to the carriers within the oven.

The plates having the coating to be dried are shown at The operation of the herein described oven is substantially as follows H In the embodiment of my invention shown in the drawings, coated or printed sheets may be delivered to the racks (Z at either or both ends of the oven, thus permitting the oven to be used as a one-way or two-way oven, as desired, the use of the hooks d permitting the sheets to be passed twice through the oven, if desired, in which event the sheets will be delivered and discharged at the same end of the oven.

The slow traverse of the carrier chains cc and the large number of racks (Z will permit all of the coated or printed sheets to be subjected for the desired interval to the action of the heated air, while giving the desired capacity to the oven.

In passing through the oven, the sheets will extend substantially vertically and will be spaced apart a distance substantially equalling that between the racks d, the guides bb relieving the chains c c from stresses due to the aggregate load of the metal sheets being conveyed thereby. WVhile a certain amount of atmospheric air will pass into the oven with the sheets, this air will be constantly replaced by heated air from vehicle of the ink or other coating, passes into the housing a from the various heating units e, the maximum heating effect of said air bysaid units being secured by compelling the air to pass about substantially the entire exterior surface of each box ff--f f of each unit by reason of the arrangement of the openings e and the air inlet at below said boxes.

Heated gases from the burner structure 71. pass successively through the boxes of each unit and gradually escape through the pipe g and flue g to atmosphere, where they cannot pollute the work room. In this manner gieat economy is secured in each heating unit, since the heated gases come into contact with a large area represented by six sides of each box 7 to f before they can escape from the casin e, said gases passing through a tortuous c annel by reason of the use and arrangement of the connecting tubes 9 before entering the pipes 9 associated with each unit and communicating with the flue pipe 9 While there Will be a material exchange ofheat through radiation from the wallsof the boxes f to f to the air flowing about said boxes, gases escaping through the pipe 9 will still have a high temperature, so that by passing this pipe=and the flue pipe 9 through the housing a, suflicient heat will be given up to the air within said housing to assist in raising the temperature of the air, Within the oven.

It will be noted that none of the products of combustion enter the housing a, so that the printed or coated plates p will not be subjected to the deleterious action of such gases.

While the oven is in use, the blower z' is continuously actuated, thus constantly withdrawing from all parts of the oven towards the top thereof, the fume-laden air arising from" the plates, this constant withdrawal of the fume-laden air also causing a continuing change in air throughout the housing a and supplementing the effect of the heating units in ensuring the desired circulation of pure, heated air adjacent the various plates p. While this circulation .will be verv slow, it will be sufli ient to avoid pocketing of air and fumes between the plates and will inducea slow circulation of air about the boxes 7 to f of the various heating units.

By arranging the openings e substantially centrally of and above the boxes f to f of each unit. the air before escaping from the unit into the housing a must pass completely about each box and across the opposite ends thereof, which are spaced away fI'OIHQthG casing e for this purpose.

\Vhile the oven is in operation, either or both rotary fans may be operated at high speed, both fans being operated when sheets are being fed to the oven at each end thereof, but only one of said fans being operated through the opening provided in the closure top j and will force it between the plates p as they pass the opening between the casing and the housing a. This air will be forced transversely of the plates, thus bringing air at a relatively much lower temperature than that of the plates and prevailing in the housing a, in contact'with the entire surface of each sheet, which at this point of the housing a will have attained its highest temperature, the sudden drop of the temperature of the sheet having the effect of giving a surface hardening to the coating material and at the same time bringing the sheet to a temperature which will permit it to be readily handled at the discharge end of the housing a.

It will be noted that each sheet willbe subjected to a blast of external air from a fan I: for a considerable period and that this air will materially assist in securing a reasonably complete oxidation of the vehicle of the ink or other coating material in addition to the cooling action thereof upon the sheet and upon said material.

The hood 7 directly opposite each .fan k will convey the air delivered by the fan h from the housing a, and since any remaining fumes about the place will be removed by the air circulated by said fam, the action of said fan will assist in keeping the air about the oven sufiicientlypure to avoid any likelihood of injurious results to the operators of the oven.

The transverse partitions 0 will limit the operative effect of the fans 70 to one reach of the carriers c0', thus permitting heated air to act upon the sheets upon the parallel adjacent portions of said carriers. l/Vhile the blast of air across the oven adjacent the d'scharge end thereof may have the effect of rawing some of the heated air from within the oven, and thus assisting the suction fan i in maintaining a circu lation of such air within the oven, this is a mere incidental effect of the fan I: and no material volume of air within the housing a will be displaced by this blast if vin fact there be any such displacement.

In a drying oven vembodying my inven tion, a secure a desired elevation in the temperature of, and about the sheets to be dried, in order to expedite the oxidation of the vehicle of the ink or other coating material. I

also secure an adequate volume of heated air circulating constantly about each sheet and avoid the presence of fumes which would interfere with the oxidizing action of the air. All fumes and roducts of combustion are excluded from t e sheets and from the room surrounding the oven which, as stated above, will not only expedite the oxidation of the vehicle of the ink or other coating, by reason of there always being an adequate supply of pure air, but will avoid the presence of noxious gases in the work room.

By using a fan is adjacent the discharge point of the oven, I am enabled to bring the sheets to a temperature sufiiciently low to permit their being readily handled in addition to securing a hardening action upon the coating, heretofore referred to.-' At the same time I am enabled to produce a much shorter oven structure while securing the same degree of oxidation of the vehicle of the ink or other coating and avoiding likelihood of the scratching of the coating as the sheets are stacked.

An oven embodying my invention has high capacity with a short length as compared with ovens in use prior to my invention, which I attribute in large measure to a provision of means for maintaining the circulation of a large volume of pure, heated air in constant engagement with the coated surface or surfaces of the sheets.

It is not my intention to limit the invention to the precise details of construction shown in the accompanying drawings, it being apparent that such may be varied without departing from the spirit and scope of the invention.

Having described the invention, what I claim as new and desire to have protected by Letters Patent, is

1. A drying gven' for printed metal sheets embodying the ein an elongated housing, an endless carrier adapted to receive low speed traverse therethrou h and including a sequence of racks close y juxtaposed and adapted to receive at spaced intervals, coated metal sheets, an enclosed heating unit within said housing,- means withdrawing the products of combustion from said heating unit-and discharging them externally of said housing, whereby contact of the products of combustion with the-coated sheets is prevented, and means circulating air about said heating unit and within said housing and discharging it externally of'the. oven, whereby fumes developed in.the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets.

2. A drying oven for printed metal sheets embodying therein an elongated housing, an

' endless carrier adapted to receive low speed trav erse therethrough and including a sequence of racks closely juxtaposed and adapted to receive at spacedintervals, Coated metal sheets, an enclosed heating unit within said housing, means withdrawing the products of combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented, means circulating air about said heating unit and within said housing and discharging it externally of the oven, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets, and means adjacent an end of said housing, whereby air at relatively lower temperature than that within the oven, is forced about the sheets upon said carrier,

whereby the temperature of the sheets is re-' housing, a plurality of communicating boxeswithin saidcasing intermediate said opening to atmosphere and the 'top of said casing, a burner within one of said boxes, a flue, and pipe connections between saidflue and said boxes, whereby the products of combustion are withdrawn directly from said boxes and not commingled with the heated air delivered to said housing, means withdrawing the products of combustion from said heating unit and discharging them externally ofsaid housing, whereby contact of the products of combustion with the coat: ed sheets is prevented, and means circulating air about saidheating unit and within said housing and discharging it externally of the oven, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets.

l. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a sequence of racks c osely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, a heating unit within said housing comprising a casing communlcating with atmosphere adjacent the bottom of the housing and at the top thereof with said housing, a plurality of communicating boxes within said casing intermediate said opening to atmosphere and the top, of said casing, a burner within one of said boxes, a flue, and pipe connections between said flue and said boxes, whereby the products of combustion are withdrawn directly from said boxes and not commingled with the housing and discharging itexternally of the oven, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets, and means adjacent an end of said housing, whereby air at relatively lower temperature than that within the oven, is forced about the sheets u on said carrier, whereby the temperature 0 the sheets is reduced, any remaining fumes are removed from about same, and. the coating material is hardened.

5. A drying oven for printed metal sheets embodying therein an elongated housing,-au en'dles carrier adapted to receive low speed traverse 'therethrough and including a sequence of racks closelyy juxtaposed and adapted to receive at spaced intervals, coated metal sheets, an enclosed heating unit within said housing, means Withdrawing the products of combustion from said heating unit and discharging them externally of said housing,whereby contact of the products of combustion with the coated sheets is prevented, an ofi'take duct adjacent the of said housing and communicating therewith at different points through a plurality of openings, and a suction pump communlcating with said duct, whereby fumes developed in the oxidation ofthe coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets.

6. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrou h and including a sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, an enclosed heating unit within said housing, means withdrawing the products of combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coatedsheets is prevent ed, an 'ofi'take duct adjacent the top of said housing and communicating therewith at different points through a pluralityof openings, a suction pump communicatlng with sa1d duct, whereby fumes developed in the oxidation of the coating material upon said sheets areremoved from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets, and means adjacent an end of said housing, whereby air at relatively lower temperature than that within the oven, is forced about the sheets upon said carrier, whereb the temperature of the sheets is reduce any remaining fumes are removed from about same, and the coating material is hardened.

7. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a sequence of s closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, a heating unit within said housing comprising a casing communicating with atmosphere adjacent the bottom of the housing and at the top thereof with said housing, a plurality of communicating boxes within said casing intermediate said opening to atmosphere and the top of said casing, a burner within one of said boxes, a flue, and pipe connections between said flue and said boxes, whereby the products of combustion are withdrawn directly from said boxes and not comgningled with the heated air delivered to sa1d housing, means withdrawing the products of'combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented, an offtake duct adjacent the top of said housing and communicating there-with at different points through a plurality of openings, and a suction pump communicating with said duct, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets.

8. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a Sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, a heating unit within said housing comprising a casing communicating with atmosphere adjacent the bottom of the housing and at the-top thereof with said housing, a plurality of communicating boxes withinsaid casing intermediate said opening to atmosphere and the top of said'casing, a burner within one of said boxes, a" flue and ipe connections between said flue and said oxes, whereby the products of com,-

bustion are withdrawn directly from 'saidboxes and not commingled with the heated air delivered to said housing, means withdrawing the products :of combustion from said heating unit and discharging 1 through a plurality of openings a suction pump communicating With said duct, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets, and means adjacent an end of said housing, whereby air at relatively lower temperature than that within the oven, is forced about the sheets upon said carrier, whereby the temperature of the sheets is reduced, any remaining fumes are removed from about same, and-the coating material is hardened.

9. A drying oven for printed metal sheets embodying therein an elongated housing, an endless-carrier adapted to receive low speed traverse therethroughand including a sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, an enclosed heating unit within said housing, means withdrawing the products of combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented, means circulating air about said heating unit and within said housing and discharging it externally of the oven, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained about the sheets, a shell adjacent an end of said housing and communicating therewith through an opening in the side wall thereof, a fan mounted within said shell directing a current of air adjacent sheets upon said carrier, and a hood oppositely disposed as to said fan, whereby air at relatively lower temperature than that within the oven, is forced about the sheets upon said carrier, whereby the temperature of the sheets is reduced, any remainin fumes are removed from about same, an the coating material is hardened.

10. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets a heating unit within said housing comprising a casing communicating with atmosphere adjacent the bottom of the housing and at the top thereof with said housing, a plurality of communicating boxes within said casing intermediate said openingto atmosphere and the top of said casing, a burner within one of said boxes, a flue, and pipe connections between said flue and said boxes, whereby the products of combustion are withdrawn directly from said boxes and not commingled with the heated air delivered to said housing, means withdrawing the products-of combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented, an ofi'take duct adjacent the top of said housing and communicating therewith at different points through a plurality of openings,' a suction pump communicating with said duct, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from within the oven, and a continuous circulation'of fresh, heated air is maintained about the sheets, said pipe connections between said flue and said boxes and said ofi take duct being positioned entirely within said housing, whereby radiant heat therefrom is utilized in maintaining high temperature within said housing, and means adj acent an end of said housing whereby air at relatively lower temperature than that within th oven, is forced about the sheets upon said carrier, whereby the temperature of 'the sheets is reduced, any remaining fumes are removed from about same, and the coating material is hardened.

11. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, a heating unit easing, tubes alternately arranged at opv posite ends of said boxes, whereby heat and heated gases will pass consecutively through all of said boxes in a series, said boxes being spaced apart by said tubes, a burner within the first box of said series, means introducing air to said box adjacent said burner, a flue, and pipe connections between said flue and the last box of said series,

whereby the products of combustion are withdrawn directly from said boxes and not commingled with the heated air delivered to said housing, means withdrawing the products of combustion from said heating unit and discharging them externally of said housing, whereby contact of the products of combustion with the coated sheets is prevented, means circulating air about said heating unit and within said housing and discharging it externally of the oven, whereby fumes developed in the oxidation of the coating material upon said sheets are remoyed from adjacent the sheets and from within the oven, and a continuous circulation of fresh, heated air is maintained} about the sheets, and means adjacent an end of said housing, whereby air at relatively lower temperature than that within the Wen, is forced about the sheets upon said carrier, whereby the temperature of the sheets is reduced, any remaining fumes are removed from about same, and the coating material is hardened.

12. A drying oven for printed metal sheets embodying therein an elongated housing, an endless carrier adapted to receive low speed traverse therethrough and including a sequence of racks closely juxtaposed and adapted to receive at spaced intervals, coated metal sheets, a heating unit within said housing comprising a casing communicating with atmosphere through an opening. arranged adjacent the bottom of the housing, a plurality of boxes within said casing intermediate said opening to atmosphere and the top of the casing, said boxes being spaced apart, tubes alternately arranged at opposite ends of said boxes,

whereby they are in communication with each other, and heat and heated gases are caused to pass consecutively through a series of such boxes, a burner within the first box of said series, means admitting air to said box adjacent said burner, a flue communicating with the last box of said series, a suction pump whereby products of combustion are withdrawn from said boxes without permitting them to commingle with the heated air in said housing, and means circulating air about said boxes and within said housing and discharging it externally thereof, whereby fumes developed in the oxidation of the coating material upon said sheets are removed from adjacent the sheets and from Within the housing, and a continuous circulation of fresh, heated air is maintained about the sheets, said casing having openings therethrough communicating with said housing substantially above the vertical center of each of said boxes, whereby inflowing air before entering said housing must pass substantially completely about each of said boxes.

In witness whereof I have hereunto aflixed my signature, in the presence of two subscribing witnesses, this 22nd day of December, 1921.

' CRLES E. MCMANUS.

Witnesses:

FRIEDA Konntnnn, SOPHIE M. BAEDER. 

